Selector switching system



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Patented May 21, 1946 UNITED STATES lPATENT oFFlcE 2,400,530 SELECTORswrromNG SYSTEM John I. Bellamy, Brookfield, Ill., assignor toA KelloggSwitchboard and Supply Company, Chicago, Ill., a corporation of IllinoisApplication April 20, 1944, Serial No. 531,949

41 Claims. (Cl. 179-18) This invention relates to selector switchingsystems, being concerned more particularly with selector switchingsystems employed at selector switching stages in automatic telephonesystems and the like to interconnect any calling incoming trunk with anidle outgoing trunk in any called numerical group.

The general object of the invention is to provide an improved selectorswitching system of.

the type employing a group of tandem-related subgrouped primary andsecondary switches.

GENERAL DESCRIPTION This invention is an improvement on the switchingsystem employed at the selector switching stage disclosed in my priorapplication for Automatic telephone switches and systems, Serial Number451,565, led July 20, 1942, now Patent No. 2,354,660, granted August 1,1944. The principal feature of improvement over thesaid priorapplicationis that the primary and secondary switches at a selectorstage are more eiciently v Fig. 9 is a modification of the selectorillustrated in Fig. 3; i I

Figs. 10 to 15 are drawings similar to Flgs.'3 to 8 respective1y, but.umstrating modined circuit arrangements for. use with a modifiedarrangement of the switching mechanism at the selector stage;

e "Fig, 16 shows the way Figs. 3 to 8 are intended to be assembled; and

Fig. 17 shows the way Figs. 10 to 15 are intended to be assembled. Theprimary and secondary switches employe in the selector system asdisclosed herein may be of the general type disclosed in my priorappli,- cation hereinbefore referred to, vbut are illustrated as of the`twenty-point, three-wire, en-

A corresponding feature of the invention is that the actfof establishinga connection from a calling incoming trunk to an idle outgoing trunk ina called numerical group, while temporarily monopolizing the primarysubgroup at which the calling incoming trunk terminates, and thesecondary subgroup at which the said idle outgoing trunk terminates,leaves all other primary and secondary subgroups free to handleothercalls.

THE DRAWINGs Other objects and features of the invention, for

the most part subordinate to those enumerated, will appear upon afurther perusal of the specication in connection with the accompanyingdrawings comprising Figs; 1 to 17, wherein;

larged-capacity type disclosed in my application for Automatic telephoneswitches, Serial No. 524,816, led March 1, 1944. l

THE PRIMARY-SECONDARY ARRANGEMENT In the modication showny in Figs. 1 to8, the primary and Secondary switches are arranged face-to-face at theselector stage, and interconnected by selector links. That is, eachprimary switch servesas the terminal point for an `incoming trunk, andhas access (in common with other switches of the same primary subgroup)to twenty selector links, and each secondary switch serves as thebeginning point of an outgoing trunk and has access (in common with theother Switches of the same secondary subgroup) to twenty selector links.

This arrangement is illustrated best in Fig. 2 wherein nine primarysubgroups of switches, A to I, are indicated and nine secondarysubgroups of switches A to I, lare indicated. Primary subgroups C to Hand secondary subgroups C to H are omitted from the drawing for thevsake of simplicity and to conserve drawing space. Since each subgroupof primary or secondary switches may have access to twenty 'A selectorlinks, the number of selector links is twenty times the number ofprimary or ySecondary subgroups. In the illustrative example, the nineprimary and nine secondary subgroups (A to I) provide for a total of 180selector links. In this arrangement, the number of selector links may yvary from forty to four hundred, according to Fig. 1 is a .call-throughdiagramshowing a connection completed from theV calling line to a calledline by way of a selector stage employing a selector system according tothe invention;

Fig. 2 is a schematic trunking diagram illustrating the generalarrangement of one embodiment 'of the improved selector system; 1

f Figs. 3 to 8 are circuit drawings of portions of the equipmentindicated in Fig. 2;

Athe traic to be carried by the primary-secondary group.of switches, forthe number of subgroups can vary from two to twenty.

The number of primary orsecondary switches .in a subgroup has more orlessfarbitrarily been set at fifteen. By this arrangement, only ilfteenof the twenty selector links served by a primary or a secondary subgroupcan be in use at the hsame time, whereby the selector links areoperatedat a very low traffic density and a consequently low lost-call rate',which, is in keeping with their comparative low cost.

In Fig. 2, the primary switches are represented by horizontal lines PAIto PAI 5 -for primary subgroup A, PBI to PBI5 for primary subgroup B,and PII to PII5 for primary subgroup I. The secondary switches arerepresented by horizontal lines SAI to SAI5 for secondary subgroup A,SBI to SBI5 for secondary subgroup B, and SII to SII5 for secondarysubgroup I. The vertical lines extending across a subgroup represent thetwenty link outlets of the subgroup by way of the twenty contact sets ofany switch in such subgroup. The common outlet (or inlet) terminals ofra subgroup are shown at the top, numbered I to 20. A few of the 180selector links are shown interconnecting primary-subgroup terminalslwith secondary-subgroup terminals. t

The nine primary subgroups, A to I, of Fig. 2, with fifteen primarytrunks each serve as' termimating points forf135 incoming trunks-Irl toITI35. Similarly, the nine secondary subgroups serve as starting pointsfor 135 outgoing trunks OTI to OTI35. The selector links are spreadbetween the primary and secondary subgroups on the basis of each primarysubgroup having access to at least one link extending to each secondarysubgroup, and vice-versa. primary and two secondary subgroups are re--quired,` half theA links from any primary subeach primary subgroup hasaccess to three links extending to each of two of the secondarysubgroups, and two links extending to each of the other seven secondarysubgroups.

The following table shows the 'general spread arrangement vfor leachnumber of primary and secondary subgroups from two to twenty:

TABLE NO. 1

No. of links from any primary subgroup to No' of subgroups the secondarysubgroups' When only two l to each.

7 each to two; 6 to one.

to each.

4 to .ach.

4 each to two; 3 each to four.

3 each to six; 2 to one.

3 each to four; 2 each to four.

3 each to two; 2 each to seven. 2 to each.

2 each tonine; 1 each to two.

2 each to eight; 1 each tofour.

2 each to seven; 1 each to six.

2 each to six; 1 each to eight.

2 each to ve; 1 eachto ten.

2 each to four; 1 each to twelve.

2 each to three; l each to fourteen. 2 each to two; l each to sixteen. 2to one; 1 each to eighteen. f 1 to each.

In carrying out any of the general spread arrangements indicated inTable No. 1, an orderly specific arrangement may be adopted wherein theselector link extending from any primary sub-A group terminal extends tothe correspondingly ment chosen and considered' preferable for thesystem of Fig. 2, wherein 180 selector links interconnect nine primaryand secondary subgroups A to I. 1 .l f

TABLE NO. 2

From From To From 'l`o S01. Sel. Sel.

pn. sec. pri. sec. pri. sec. hnk term. term. 'lfmk term. term. lmk term.term.

l 1 B1 B1 41.--. C1 C1 V1 B2 B2 42.... o2 C2` 3 B3 B3V 43.--. C3 C3 4 B4C4 44.... C4 D4 5 B5 C5 45.-.. C5 D5 6 B6 C6 46..-. C0 Dfi 7 B7 D747.-.. C7 E7 8 B8 .D8 48.... C8 EX v9 B9 E9 49.... C9 F9 1 B10 E1050.... C10 F10 B11 F11 `51.... C11 G11 B12 F12` 52 C12 GIZ B13 G1353.-.. C13 1113 B14 G14 54.-.. C14 H14 B15 H15 55.--. C15 115 B16 1116'56.-.. C16 116' B17 117 57...- C17 A17 v13118 118 58.--. C18 A18 B19 A1959.-.. C19 B19 B20 A20 60--.. C20 B20 From To From To From To Sel. Sel.Scl.

. pn. sec. pn. sec. pri. sec. lmk term. term. lmk term. term lmk term.term.

61.... D1 D1 81.--. E1 E1 101.- F1 F1 62.... D2 D2 82---. E2 E2 102.- F2F2 63... D3 D8 83.-.. E3 'E3 103... 4 F3 F3 64.... D4 E4 84---. E4 F4104-.. F4 G4 6. D5 E5 8. E5 F5 105.-- F5 (15 60.-.. D6 E6 86---. E6 F6106..- IF6 G6' 67.... D7 F7 87--.. 7 G7 107... F7 H7 68.... D8 F8 88....E8 G8 108... F8 118 69.... D9 G9 89.... E9 H9 109... F9 `I9 70.--. D10G10 90.-.. E10 AH10 110.-- F10 110 71.-.. D11 H11 91.-.- 'E11 111 111.-.F11 A11 72.-.. D12 IIZ 92.--. E12 112 112.-. F12 Alf? 73-.-. D13 11393---- E13 A13 113.-. F13 B13 74...` D14 114 94---. E14 A14 114... F14B14 75.-.. D15 A15 95.--- E15 B15 115... F15 C15 76.--- D16 A16 9s E10IB16 116.-- El C162 77..-. D17 B17 E17 C17 117...- F17 D17 78..-. l D18B18 E18 C18 118.-. F18 D18 79..-. D19 C19 E19 D19 119.-. F19 E19 80.-..D20 C20 E20 D20 120--. F20 E20 From To From To From To Sel. Sel. Scl.

. pri. sec. pri. sec. pri. sec. kuk term term. hnk term. term. hnk term.term.

121... G1v G1 141--- Hl H1 I1 I1 122... G2 G2 142.-- H2 H2 12 12 123...G3 G3 143--. H3 113 13 I3 124... G4 H4 144. H4 I4 I4' A4 125... G5 H5145.-- H5 I5 15 A5 126... G6 H6' 146... H6 16 I0 .lli 127--. G7 I7147--- H7 A7 I7 v117' 1 128.-. G8 I8 148--- H8 A8 I8 B8 129--. G9 A9149-1-- H9 B9 I9 C9 130..- G`10 A10 150.-- H10 B10 110 C10 131.-. G11B11 151-.. H11 C11 111 D11 132... G12 B12 152... H12 C12 112 DIL'.133--- G13 C13 153.-. H13 D13 113 E13 134.-. G14 C14 154.-- H14 'D14 114E14 135 G15 D15 155..` H15 E15 115 F15 136.-. G16 D16 156--. H16 E16 116Fili 137..- G17- E17- 157--. H17 E17 117 G17 138... G18 E18 158--. H18F18 .118 G18 139... G19 F19 159.-- H19 G19 119 H19 140-.- G20 I.F20160--- H20 G20 120, ...1120

NUMERIcAL GROUPING oF OU'rcorNG TRUNKs 1, 2 and 0 are representedrespectively by cables 2||,2I2,and22|'i.

For convenience in' grouping, the outgoing Atrunks OTI to OTI35 may bepassed through an intermediate distributing frame indicated at IDF,across whichv each trunk may be carried by a separate jumper connection.The preferred astrunks, or fewer, while other numerical groups maycontain twenty trunks or more, all depending upon the trailicrequirements.

THE GROUP-CONTROL ARRANGEMENT In the arrangement shown in Fig. 2, tengroup A controllers, GCI to GCU, correspond respectively to the tennumerical groups of outgoing trunks. Each group controller is arrangedvto direct any primary switch in any subgroup to extend a connection toany outgoing trunk in the corresponding numerical group, by wayof aselector link and the concerned secondary switch. Any operating groupcontroller is assisted in selection of an idle outgoing trunk by one oranother of the nine secondary controllers SCA to SCI, according to thesecondary subgroup through which connection with an idle trunk i'n thecalled numerical group is located. The secondarycontrollers areconnected with the group controllers throughl the nine cables to '|I9.Since each secondary subgroup has its own secondary controller, eachsecondary subgroup is able to act as aunit independent of the others.

THE SELECTORS includesan arrangement of control relays (Fig.

3) for performing theI necessary' control functions, and fortransmitting impulses to a register device, through which selection ismade of one or another of ten so-called dialleads, one for each separatedigit value employed to direct a call through the selector stage. tendigit values is employed for each of the ten -numerical groups 1 to 0 ofoutgoing trunks.

Each subgroup of selectors is provided with ten connecting relays, suchas relays 40| to 4I0 of subgroup A, in which the dial leads DLI to DLOof that selector subgroup terminate. Through the selection and operationof one or another of the relays 40| to 4 I 0, connection is made withthe A separate one of corresponding one of the group controllers GCI toGCU, by way of a local cable such as 450 and set of dial leads such asDLI to DLO, its own group of ten connecting relays such ets-40| to 4|0,and its own local cable such as 450, each selector subgroup, togetherwith its associated primary subgroup of switches, is Yable to act as aunit independent of the` others.

THE CIRCUIT DnAwI-Nos IIhe circuit drawings of Figs. 3 to 8 will now beexplained brieily. Fig. 3 shows in full the circuits of selector SEL-AIand indicates the Ilf- `teenth selector SEL-AIS by means of a rectangle.

intermediate selectors, form selector subgroup A These two selectors,together with thirteen tor. l

Fig. 4 shows three of the ten connecting relays 40| to 4|0 to which thedial leadsDLi to DLI) of selector subgroup A respectively extend. Eachsuch relay, when. operated over its associated dial lead from anyselector in selector subgroup A,

operates to interconnect conductors 3|0, 3| I, and the conductors insubgroup-A cable 450, to conductors in the associated one of the cables42| to 430 extending respectively to the ten group controllers GC! toGCU.

Fig..5 shows the circuit arrangement of primary subgroup A of Fig. 2,primary switches PAI v and PAI 5 beingv shown.j The intermediate pri--mary switches ofv this subgroup are omitted to conserve drawing\\space.Primary switch PAI,

for example, contains eleven selective stackups of the stackups ofcontacts 1 to 11. The select magnets for stackups 1, 2, 10, and 11 aremagnets 52|, 522, 530, and 53|. Select magnet 53|, associated withstackup 11 of.any primary switch of the subgroup, is operated or not(along with one of the magnets 52|y to 530) depending upon whether thelower contact set or the upper contact set of an operated stackup 1 to10 is to be effective.

For the operation, and maintenance, of the` selected combination ofstackups, each switch is provided with a hold magnet (50| for switchPAI,

and 5|5 for switch PAIS) The off-normal stackup ON of' any of theswitches is not a selective stackup, being operated each time thecorresponding hold magnet,

such as 50|, is energized, irrespective of what stackup selection hasbeen accomplished.'

Each primary and each secondary subgroup or switches is provided withits own set of select magnets 52| to 53|, and with its own set ofselecting shafts (not shown), whereby each subgroupfis capable ofoperating as a unit independent of the other subgroups.

Fig. 6 is a drawing corresponding generally to Fig. 5, butshowingsecondary subgroup A instead of primary subgroup A. Here again,only the first and niteenth switches are shown, and stack- That is, l

Y similar.

4ups 3 to 9 are omitted. Magnets 62| to sal cor- Assuming the primaryand secondary sub-- groups to b mounted in superposed relation asindicated in Fig. 2, spread cable 600 extends vertically between themand has lateral branches for the respective primary and secondarysubgroups, Branches PA and SA are the lateral branches for primarysubgroup A and secondary subgroup A. rIhis spread cable containsconductor sets comprising the selector links interconnecting thesubgroups vof primary and secondary switches according to Table No. 2,appearing hereinbefore. Each selector link (such as SLI to SL20extending from primary subgroup A) includes four conductors, a magnetconductor M, andthe usual tip, ring, and sleeve conductors i T, R, andS. The magnet conductor M in any selector link is the conductor overwhich the one of the ten select magnets lsuch as 62| to 630 is operatedin the secondary subgroup to which such link extends, Awith or withoutoperation of the associated eleventh select Amagnet such as 63|.

The six contact pairs instackups 1 to 10 of any switch comprise an upperset of three and a lower set of three, each switch having ten upper setsand ten lower sets. lThe upper sets represent terminals l to 10,respectively, of the subgroup, while the lower sets represent terminals11 to 20, respectively. Stackup 11 of any switch .is operable to rendersets 11 .to 20 effective in place of sets 1 to 10.l

Fig. 7 shows the circuit arrangement at group controller GCI of Fig. 2,the circuit arrangement at each of the other group controllers beingGroup controller GCI includes 'start and test relays 'IOI and "|02, a'pair of busy relays 103 and y 104, a pair of preference-shift relays |05and 106, and twenty-seven link-test relays IA to 31. The

llink-test relays are assigned inl subgroups of three to test the linksextending from a calling primary subgroup to the respective secondarysubgroups. 'I'his is in accordance'with Table No. 2, 'wherein it will benoted that not more than threel selector links extend from any primarysubgroup to any secondary subgroup. Relays IA to 3A are assigned tolinks extending from-a calling primary subgroup to secondary subgroup A;relays IB to 3B ,are assigned to links extending to. secondary subgroupB; and so on, to relays II to 3I, which are assigned to links extendingfrom a ycalling primary subgroup to secondary subgroup I. l

Group controller GCI is connected with selec- I tor subgroups A to 'I bythe conductors in cable 42| incoming to Fig. '7 from Fig. 4. Groupcontroller GCI is also interconnected with the nine secondarycontrollers (SCA to SCI), by conductor sets IA, IB, and so forth, to II,lying respectively in cables |II to 'II9. These cables carry similarconductor sets to the secondary controllers from the other groupcontrollers. AThese other conductor sets (not shown in Fig. 7) may besimilarly labeled 2A to 2I, 3A to 3I, and so forth, to 0A to 0I,according lto the groupI controller at which they originate.

line ITI incoming to the selector stage.

Fig. 8, comprising' parts I and`2, shows secondary controller SCA ofFig. 2. the otherl secondarycontrollers being similar. Relays TI to TI5are test relays corresponding respectively to the iifteen trunks, OTI toOTI5, outgoing 4from the associated secondary subgroup A. The in-Iterconnection between the outgoing trunks and relaysfTI to TI5 isthrough conductors SI to SI5 in cable 650, and by way of contacts ofconnecting relay 02 I when operated.

Relays to 8I0 are numerical-group relays assigned respectively tonumerical groups 1 to 0 of outgoing trunks.v Each such numerical-grouprelay is controllable only from the corresponding group controller, andthen only if the secondary controller is idle. Upon the operation of anynumerical-group relay, Voperations occur to mark the secondarycontroller busy to the remaining group controllers, fas will-'i appearsubsequently, and to initiate the operation o'f the switching apparatusto complete the connection.

DETAILED DESCRIPTION Referring now particularly to Fig. 1, the generaloperations involved in setting up a connection from a calling substationA to `a called substation B will now be described. y

When the -receiver (notshown) is removed at substation A, adirect-current bridge is estab-v lished across the tip and ringconductors of the associated line, operating line relay IOI throughcontacts of cutoff relay, I02'to cause nder action to occur at theassociated nder stage.` As a result of this finder action, the tip,ring, and sleeve conductors of the calling line are extended in anydesired manner to an idle trunk line such as trunk ITI, it may bepointed out, is shown also in Fig, 5, incoming to the primary switchPAI. line ITI 'is normally marked idle by an idle-indicating batterypotential applied to the sleeve conductor S thereof by way of contactsof release relay 302 and contacts in stackup ON of the associatedprimary switch PAI, the connection being made by way of the illustratedcurrent-limiting resistor,...

When the finder-stage extension has been made,

.line relay 30| associated with trunk ITI (being a relay -of selectorSEL- AL Fig. 3) operates over the calling line, causing operation of theassociated release relay 302. Relay 302 disconnects the normally appliedidle-indicating battery potential and substitutes ground potential tomaintain in the usual manner the connection establishedI through thefinder stage, closing arr'operating circuit 'for cutoff relay |02. Relay|02 thereupon operates to disconnect the line-relay bridge, whereuponline relay IOI restores.

The calling subscriber may now dial the rst digit in the number assignedto the line of substationi B, causing the usual series of interruptionsto be produced in the bridge across the calling line by the usual formof calling device. The resulting series of momentary restorations ofline relay 30| causes a Vselecting operation to occur in a manner to beexplained subsequently in connection with Fig; 3. Upon the terminationof the dialing of this digit, operations occur to test the selectorlinks such as SLI accessible to pri- The trunk

